/*!
 * Crypto-JS v1.1.0
 * http://code.google.com/p/crypto-js/
 * Copyright (c) 2009, Jeff Mott. All rights reserved.
 * http://code.google.com/p/crypto-js/wiki/License
 */
(function() {

  // Shortcut
  var util = Crypto.util;

  Crypto.PBKDF2 = function(password, salt, keylen, options) {

    // Defaults
    var hasher = options && options.hasher || Crypto.SHA1,
      iterations = options && options.iterations || 1;

    // Pseudo-random function
    function PRF(password, salt) {
      return Crypto.HMAC(hasher, salt, password, {
        asBytes: true
      });
    }

    // Generate key
    var derivedKeyBytes = [],
      blockindex = 1;
    while (derivedKeyBytes.length < keylen) {

      var block = PRF(password, salt + util.bytesToString(
        util.wordsToBytes([blockindex])));

      for (var u = block, i = 1; i < iterations; i++) {
        u = PRF(password, util.bytesToString(u));
        for (var j = 0; j < block.length; j++) block[j] ^= u[j];
      }

      derivedKeyBytes = derivedKeyBytes.concat(block);
      blockindex++;

    }

    // Truncate excess bytes
    derivedKeyBytes.length = keylen;

    return options && options.asBytes ? derivedKeyBytes :
      options && options.asString ? util.bytesToString(derivedKeyBytes) :
      util.bytesToHex(derivedKeyBytes);

  };

})();
